重庆周缘龙马溪组和牛蹄塘组页岩有机质孔隙发育特征

针对牛蹄塘组页岩气勘探开发过程中存在产气量较低，产气持续时间较短等问题，以渝东南下志留统龙马溪组页岩和渝东北下寒武统牛蹄塘组页岩为对象进行对比，重点剖析2套页岩的孔隙储集能力及其演化特征。结果表明：龙马溪组页岩和牛蹄塘组页岩的有机质孔隙发育特征存在较大差别：龙马溪组页岩内部的固体干酪根有机质孔隙数量少，孔径小，连通性差，但其焦沥青内部有机质孔隙数量多，孔径大，连通性好。牛蹄塘组页岩内部的固体干酪根和焦沥青均不发育有机质孔隙。储层热演化程度对页岩有机质孔隙的发育有着直接的控制作用。龙马溪组页岩由于古埋深较牛蹄塘组页岩浅，所经历的热演化作用相对较弱，适宜的热演化程度保留了龙马溪组页岩焦沥青内部大量的有机质孔隙，但其固体干酪根由于演化时间相对较长，有机质孔隙数量减少。渝东北牛蹄塘组页岩埋深过大，储层过度演化达到变质期导致其内部固体干酪根和焦沥青均不发育有机质孔隙。针对牛蹄塘组页岩气的高效勘探开发应寻找热演化程度适中的页岩分布区。

Organic pore development characteristics of Longmaxi and Niutitang shales in the periphery of Chongqing

In the exploration and development process of shale gas in Niutitang Formation, there are problems such as low gas production and short duration. By comparing the Lower Silurian Longmaxi shale in southeastern Chongqing with the Lower Cambrian Niutitang shale in northeastern Chongqing, the pore reservoir capacity and evolution characteristics of the two sets of shale were analyzed. The results show that there are significant differences in organic pore development characteristics of the Longmaxi shale and the Niutitang shale. The organic pores inside solid kerogen in the Longmaxi shale have a small number, small pore size and poor connectivity, but the amount and size of organic pores in pyrobitumen are large, and the connectivity is good. The solid kerogen and pyrobitumen in the Niutitang shale do not develop organic pores. The degree of reservoir thermal evolution has a direct control effect on the development of organic pores in shale. The Longmaxi shale is relatively weak in thermal evolution as palaeo-buried depth is shallower than the Niutitang shale. The appropriate degree of thermal evolution preserves a large amount of organic pores in the pyrobitumen of the Longmaxi shale, but the solid kerogen has a relatively long evolution time and the number of organic pores decreased. The palaeo-buried depth of the Niuzhitang shale in northeastern Chongqing is too large, and reservoir reached the metamorphic period due to excessive evolution, resulting in the absence of organic pores in the solid kerogen and pyrobitumen. For the efficient exploration and development of shale gas in the Niutitang Formation, a shale distribution area with moderate thermal evolution should be sought.